doi:10.1038/nindia.2016.141 Published online 24 October 2016
New observational data from India’s GRAPES-3 cosmic-ray telescope in Ooty indicate that Earth’s polar magnetic field temporarily weakened during a severe geomagnetic storm triggered by the solar flare on 21 June 2015. This created a ‘crack’ or opening in the protective shield allowing an unusually high flux of harmful cosmic rays into the magnetosphere — a 2-hour-long cosmic-ray shower on Earth, researchers report1.
Earth’s magnetic field deflects most cosmic rays, protecting living things from harmful radiation. But large geomagnetic storms, following solar flares, can reconfigure this protective shield, opening up weak spots that let radiation and cosmic rays slip through.
Numerical simulations performed by the GRAPES-3 collaboration, which includes researchers from India and Japan, suggest that this is exactly what happened following the 2015 solar flare incident.
The transient weakening of Earth’s magnetic shield observed by the GRAPES-3 telescope "may hold clues for a better understanding of future superstorms that could cripple modern technological infrastructure on Earth, and endanger the lives of the astronauts in space," the report says.
1. Mohanty, P. K. et al. Transient Weakening of Earth’s Magnetic Shield Probed by a Cosmic Ray Burst. Phys. Rev. Lett. 117, 171101 (2016) doi: 10.1103/PhysRevLett.117.171101